Particle size of drugs and its relationship to absorption and activity

Toxicological assessment of photoactivated tetra-cationic porphyrin molecules under white light exposure in a Caenorhabditis elegans model

Photodynamic therapy (PDT) utilizes the potential of photosensitizing substances to absorb light energy and produce reactive oxygen species. Tetra-cationic porphyrins, which have organic or coordination compounds attached to their periphery, are heterocyclic derivatives with well-described antimicrobial and antitumoral properties. This is due to their ability to produce reactive oxygen species and their photobiological properties in solution. Consequently, these molecules are promising candidates as new and more effective photosensitizers with biomedical, environmental, and other biomedical applications. Prior to human exposure, it is essential to establish the toxicological profile of these molecules using in vivo models. In this study, we used Caenorhabditis elegans, a small free-living nematode, as a model for assessing toxic effects and predicting toxicity in preclinical research. We evaluated the toxic effects of porphyrins (neutral and tetra-cationic) on nematodes under dark/light conditions. Our findings demonstrate that tetra-methylated porphyrins (3TMeP and 4TMeP) at a concentration of 3.3 µg/mL (1.36 and 0.93 µM) exhibit high toxicity (as evidenced by reduced survival, development, and locomotion) under dark conditions. Moreover, photoactivated tetra-methylated porphyrins induce higher ROS levels compared to neutral (3TPyP and 4TPyP), tetra-palladated (3PdTPyP and 4PdTPyP), and tetra-platinated (3PtTPyP and 4PtTPyP) porphyrins, which may be responsible for the observed toxic effects.

Nanoparticles of biotite mica as KrishnaVajraAbhraka Bhasma: synthesis and characterization

Background

Bio-inorganic nanoparticles or metal nanoparticles are used in medicine for diagnostic and treatment purposes. The nanomedicines from traditional Ayurvedic system are termed as bhasma. Rasashastra, the branch of inorganic medicines of Ayurveda, has documented monographs of metal-mineral bhasmas as potent drugs. However there is lack of scientific analytical data of the end products.

Objectives

Present study was aimed at finding out the morphological, structural, elemental and chemical composition of the Krishna vajra abhraka bhasma (KVB).

Materials and methods

Bhasma of KVB (Biotite Mica) was prepared in our laboratory using biotite mica sheets befitting selection criteria and carrying out further processes with strict SOPs as per AFI.

Results

The bhasma complied with the confirmatory tests from Rasashastra. The physical and physicochemical tests correlate with the results obtained by instrumental analytical methods. SEM revealed square shaped nanoparticles of mean size of 92.3 nm. EDAX showed presence of Si, Mg, O, Fe, Ca, Na, C, K and Al. XRD revealed the crystalline nature of bhasma with mixture of various individual oxides and spinel shape of the crystal. DLS showed that the nanoparticles are unimodal in nature. FTIR and NMR showed the organic functional groups obtained from cow milk and selected herbs, indicating unique bio-inorganic nature of the KVB.

Conclusion

The therapeutic potential imparted to the formulation could be due to the cow milk and specific herbs utilized during the manufacturing process.

Rutin nanosuspension for potential management of osteoporosis: effect of particle size reduction on oral bioavailability, in vitro and in vivo activity

Clinical significance of Rutin (RUT) is limited by poor dissolution rate and low oral bioavailability. The study was designed to improve the physicochemical and therapeutic potential of the drug by formulating nanosuspension (NS) for osteoporosis. Rutin nanosuspension (RUT-NS) was prepared after screening a range of stabilizers and their combinations at a different concentration by antisolvent precipitation technique. Effect of precipitation on crystallinity (differential scanning calorimetry DSC, X-ray diffraction studies XRD), morphology (scanning electron microscopy, SEM) and chemical interaction (attenuated total reflectance fourier-transform infrared spectroscopy ATR-FTIR) were studied through biophysical techniques. An optimized nanosuspension exhibited a minimum particle size of 122.85 ± 5.02 nm with higher dissolution of RUT-NS (87. 63 ± 2.29%) as compared to pure drug (39.77 ± 2.8 6%). The enhanced intestine absorption and apparent permeability were achieved due to the improved particle size, surface area and dissolution. RUT-NS displayed greater (3 folds) AUC_0-24 h than pure drug. In vitro assays with RUT-NS depicted an increased cell proliferation, antioxidant (ROS) activity and osteocalcin production in MG-63 osteoblast cells. The augmented biochemical in vivo biomarkers and bone quality proved the protective effect of RUT-NS. The results supported RUT-NS as a potential therapy for maintaining bone health.

Enhanced Biopharmaceutical Performance of Rivaroxaban through Polymeric Amorphous Solid Dispersion

Rivaroxaban (RXB) is an orally active direct inhibitor of the activated serine protease Factor Xa, given as monotherapy in the treatment of venous thromboembolism (VTE). It has been characterized in vitro as a substrate for the active, nonsaturable efflux via P-gp transporter, limiting its high permeability. Therefore, the role of P-gp inhibiting polymers in enhancing the biopharmaceutical performance of RXB by preparing polymeric amorphous solid dispersion and subsequent improvement in solubility and permeability was investigated. Initially, solubility parameter and Flory-Huggins interaction parameter were determined for miscibility studies between drug and polymers. Binary dispersions were prepared by dissolving drug with polymers eudragit S100, eudragit L100, and soluplus in common solvent (5% v/v water in tetrahydrofuran) using spray dryer. Prepared binary dispersions were analyzed by differential scanning calorimetry (DSC), microscopy, powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FTIR), dynamic vapor sorption (DVS), and solution nuclear magnetic resonance (NMR) spectroscopy. Superior performance of binary dispersions was observed upon dissolution and solubility studies over micronized active pharmaceutical ingredient. Amorphous solid dispersion (ASD) prepared with soluplus showed 10-fold increase in apparent solubility and maintenance of supersaturation for 24 h compared to the crystalline RXB. Further, pharmacokinetic study performed in animals was in good correlation with the solubility data. Increases of 5.7- and 6.7-fold were observed in AUC and C_max, respectively, for ASDs prepared with soluplus compared to those with crystalline RXB. FTIR and NMR spectroscopy unveiled the involvement of N-H group of RXB with C═O group of polymers in intermolecular interactions. The decreased drug efflux ratio was observed for ASDs prepared with eudragit S100 and soluplus in Caco-2 transport study suggesting improvement in the absorption of RXB. Hence, the present study demonstrates ASD using soluplus as a promising formulation strategy for enhancing the biopharmaceutical performance of RXB by increasing the solubility and circumventing the P-gp activity.

Oral bioavailability enhancement of β-lapachone, a poorly soluble fast crystallizer, by cocrystal, amorphous solid dispersion, and crystalline solid dispersion

The aim of this paper was to compare the in vitro dissolution and in vivo bioavailability of three solubility enhancement technologies for β-lapachone (LPC), a poorly water soluble compound with extremely high crystallization propensity. LPC cocrystal was prepared by co-grinding LPC with resorcinol. LPC crystalline and amorphous solid dispersions (CSD and ASD) were obtained by spray drying with Poloxamer 188 and HPMC-AS, respectively. The cocrystal structure was solved by single crystal x-ray diffraction. All formulations were characterized by WAXRD, DSC, POM and SEM. USP II and intrinsic dissolution studies were used to compare the in vitro dissolution of these formulations, and a crossover dog pharmacokinetic study was used to compare their in vivo bioavailability. An 1:1 LPC-resorcinol cocrystal with higher solubility and faster dissolution rate was obtained, yet it converted to LPC crystal rapidly in solution. LPC/HPMC-AS ASD was confirmed to be amorphous and uniform, while the crystal and crystallite sizes of LPC in CSD were found to be ∼1-3 μm and around 40 nm, respectively. These formulations performed similarly during USP II dissolution, while demonstrated dramatically different oral bioavailability of ∼32%, ∼5%, and ∼1% in dogs, for CSD, co-crystal, and ASD, respectively. CSD showed the fastest intrinsic dissolution rate among the three. The three formulations showed poor IVIVC which could be due to rapid and unpredictable crystallization kinetics. Considering all the reasons, we conclude that for molecules with extremely high crystallization tendency that cannot be inhibited by any pharmaceutical excipients, size-reduction technologies such as CSD could be advantageous for oral bioavailability enhancement in vivo than technologies only generating transient but not sustained supersaturation.

Study on Bioavailability of Sulfadiazine Tablets in Man

Sulfadiazine Tablets USP, 500 mg, from 3 different manufacturers were tested in vitro and in vivo. Dissolution rate and disintegration time were measured in water, artificial gastric fluid, and artificial intestinal fluid. Disintegration and dissolution were fastest in artificial gastric fluid. Product I was superior in disintegration to the other two products, whereas product 2 was superior in dissolution. The in vivo study was designed as a Latin square so that each of the 3 treatments was given to each of the 3 subjects at each of the 3 time periods. Two-way analysis of variance was done using the cumulative urinary excretion of free and total sulfadiazine after 24 and 120 hours. Although the extent of bioavailability of product 1 and 2 was only 78 and 73 percent, respectively, statistically significant differences were found only at 24 hours. Judging from both rate and extent of bioavailability, product 3 was superior to products 1 and 2. The difference between in vitro and in vivo data is noted.

Co-milling of telmisartan with poly(vinyl alcohol)--An alkalinizer free green approach to ensure its bioavailability

The aim of this study was to enhance the dissolution and bioavailability of telmisartan (TLM), a poorly water soluble drug by co-milling approach. Physical mixtures of TLM and poly(vinyl alcohol) (PVA) were co-milled in a planetary micro mill in a dry condition by varying process parameters such as drug to polymer weight ratio, ball-to-powder weight ratio, and rotational speed. The co-milled products offered cumulative percentage dissolution of TLM above 75% in 30 min (CG 1 and CG2). These samples were characterized using field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and Raman spectra analysis. Well-dispersed acicular shaped particles of TLM were observed in co-milled products. A mixture of crystalline and amorphous TLM with a particle size less than 1 μm was present in CG1. The particle size of TLM observed in CG2 was less than 2 μm. In addition to crystalline and amorphous form of TLM, defective/disordered crystals of TLM were also present in CG 2. Therefore, CG2 tablets exhibited poor stability. CG 1 tablets were found to be stable under accelerated stability test conditions. The relative bioavailability of TLM of CG 1 containing tablets in comparison with Micardis® was 93.92±12.84% (in rabbits). Thus, co-milling of TLM with PVA proves to be a promising "alkalinizer free green approach" to ensure the dissolution and bioavailability of poorly water soluble TLM.

Effect of the granulometric characteristics of monensin sodium on controlling experimental coccidiosis in broiler chickens

The aim of the present study was to investigate the efficacy of monensin sodium grain size on controlling coccidiosis in broiler chickens. Three hundred and fifty Cobb 700 chicks were infected experimentally with 8 × 10(4) sporulated oocysts of Eimeria spp. The birds were fed with diets supplemented with powdered (n = 150) or granulated (n = 150) monensin, with particle sizes of ≤ 100 µm and 450-650 µm, respectively. The remaining chicks (n = 50) were used as an unmedicated control group. The birds' weights and number of oocysts per gram of litter in each group were recorded weekly. A total of 96 birds were randomly selected and culled during the trial. Their intestinal oocyst counts and lesion scores were determined. No significant differences in body weights were found between the groups at the end of the study. The percentages of infected animals, oocyst counts and lesion scores were significantly higher in the control group than in the other two groups; the two treated groups did not show any appreciable differences to each other. Enteritis was observed in 14 birds, all in the group supplemented with granulated monensin. These results suggest that powdered and granulated monensin have comparable efficacy in controlling coccidiosis in broiler chickens. However, treatments with monensin sodium of high grain size may be subject to contraindications relating to enteritis.

Comparison of cefpodoxime proxetil release and antimicrobial activity from tablet formulations: complexation with hydroxypropyl-β-cyclodextrin in the presence of water soluble polymer

This study aims to prove the complexation of cefpodoxime proxetil (CP) by hydroxypropyl-β-cyclodextrin (HP-β-CD) in the presence of sodium carboxymethyl cellulose (Na CMC), and makes a comparison of commercial tablets by dissolution and antimicrobial activity studies. The CP--HP-β-CD complex was prepared by kneading method and characterized by SEM, FTIR and DSC. The solubility method was used to investigate the effect of HP-β-CD and Na CMC on the solubility of CP. The complex tablets were prepared using direct compression method. Dissolution studies were performed with complex tablets and commercial tablets in pH 1.2, 4.5, 6.8 and 7.4 buffer solutions. It was observed that complexation occurred in all formulations, and HP-β-CD is able to increase CP solubility and dissolution rate of CP was improved from complex tablets, when compared with commercial tablets. Furthermore, the antimicrobial activity studies revealed that the CP--HP-β-CD complex and complex tablets were shown to have more effective antimicrobial activity than commercial tablets. It is evident from the results that complexation with HP-β-CD in the presence of Na CMC is feasible way to prepare a more efficient tablet formulation with improved dissolution and antimicrobial activity.

In vitro assessment of ampicillin capsules marketed in Nigeria

An in vitro characterisation of thirteen brands of 250mg ampicillin capsules available in Nigeria was carried out. Nearly a quarter (3; 23.1 per cent) of the brands tested were substandard. Two brands, one from England, failed the BP identification test for ampicillin and were classed as fakes. Eleven brands passed the BP uniformity of weight and disintegration tests, but only 10 brands passed both the BP content uniformity test and the BP dissolution rate test. Similar dissolution profiles for three brands of ampicillin capsules were obtained with three different pieces of equipment — the BP apparatus, Levy's beaker apparatus and a stationary basket/magnetic stirrer apparatus. The results emphasise the need for routine quality assurance testing of pharmaceuticals before dispensing to patients. The stationary basket/magnetic stirrer dissolution test has the advantage of simplicity and low cost.

Optimization of the operating conditions of a lab scale Aljet mill using lactose and sucrose: a technical note

The results of the experiments have revealed that the optimal operating conditions for a lab scale Aljet mill are at the high level (110 psi) of the pushing nozzle and the low level (65 psi) of both grinding nozzles, or vice versa. Operating the Aljet mill at high pushing and grinding pressures also produces small particle size; however, the high pressures require more gaseous fluid making the process less efficient. At a very low pushing nozzle pressure as compared with the grinding nozzle pressure, the material kicks back from the mill, reducing the yield. Optimization of the lab scale Aljet mill operating conditions will be very useful in particle size reduction of poorly water-soluble compounds and is particularly beneficial at early stages of drug development when the drug quantity is very limited.

A computational model for particle size influence on drug absorption during controlled-release colonic delivery

The effect of particle size on the percent drug absorbed is computationally modeled for controlled-release dosage forms that deliver drug particles to the colon. The relative benefit of reducing particle size is mapped on a diagram of the drug's absorption rate constant (estimated from rat intestinal perfusion, CACO-2 or human intubation permeation rates) versus the drug's solubility. Some drugs fall into a limit of high percentage absorption even with large particles such that particle size reduction has little impact. Another group of drugs is solubility limited such that even with small particles, absorption is negligible. Between the two regions, only drugs with sufficiently high absorption rates are influenced by the drug dissolution rate and thereby the particle size. The size of this region is a function of dosing rate. Comparisons between calculated particle size effects on colon absorption as a function of colon volume suggest caution when using animal models to predict bioavailability from colonic drug delivery. This volume dependence also suggests that the particle size influence will vary as a function of the digestive cycle.

Fast- and slow-release tablets for oral administration of flavonoids: rutin and quercetin

Many derivatives of rutin (Rt) and its metabolite quercetin (Q) are employed in clinics for cardiovascular chronic pathology, and are also known for their antiulcer behavior in vivo and antiproliferative and antimutagenic activity in vitro. Unfortunately, the absorption of quercetin and rutin from the gastrointestinal tract is slow and irregular, probably due to their very slight solubility in water and slow dissolution rate. In this work the dissolution rate of the drugs from oral formulations has been improved using some enhancers such as cross-linked sodium carboxy, methylcellulose (CMC-XL), sodium carboxymethylstarch (E), and cross-linked polyvinylpyrrolidone (P). The drugs were loaded on the hydrophilic carriers by different techniques such as mixing or co-milling. The in vitro dissolution profiles of the mixed or co-milled drug/polymer systems, obtained in various media with different pH, were compared. The results show that the drug dissolution rate from the co-milled drug/carrier systems is faster than that from mixed systems, and CMC-XL and sodium carboxymethylstarch systems are able to enhance the dissolution rate. For this reason, these co-milled drug/carrier systems were used for the production of both fast- and slow-release tablets. The co-milled drug/CMC-XL system was used for the preparation of fast-release tablets containing rutin, while three different fast-release tablets were formulated and tested using respectively Q/CMC-XL, Q/E, and Q/P co-milled systems. The effect of the presence of sodium lauryl sulfate in the aqueous medium on the dissolution profile of flavonoids alone was also studied. The prolonged-release formulations have been developed using hydroxypropylmethylcellulose (HPMC) of different viscosity grades as retarding polymer. An extended release of the drugs for times ranging from 6 to 14 hr could be obtained, depending on the type and viscosity of the HPMC used.

Dissolution properties of piroxicam powders and capsules as a function of particle size and the agglomeration of powders

The poor dissolution characteristics of relatively insoluble drugs have long been a problem to the pharmaceutical industry. An example is piroxicam, a highly potent anti-inflammatory agent. In many countries, a large number of generic piroxicam products are available to the prescriber. The aim of this study was to investigate the cause of the dissolution problems experienced by manufacturers of generic piroxicam capsules. Two raw material batches and the dissolution properties of several piroxicam capsules were studied. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) results showed that the two raw material samples were identical with respect to polymorphic modification. The particles of powder 1 were smaller than those of powder 2, but the dissolution of powder 1 was much slower than that of powder 2. The dissolution results for the capsules showed a marked difference among different brands, with capsule C not meeting the USP tolerance. Adding surfactant to the dissolution medium increased the dissolution of both powder 1 and capsule C. Failure of powder 1 or capsule C to meet USP dissolution criteria could result in differences in product efficacy, as well as in potential side effects. Such observations should be taken into account along with other relevant considerations when decisions regarding the generic substitution of oral piroxicam products are made.

Development of anti-influenza virus drugs I: improvement of oral absorption and in vivo anti-influenza activity of Stachyflin and its derivatives

PURPOSE

Stachyflin and its derivatives which are active against the influenza virus in vitro, were studied to improve their reduced in vivo activity after oral administration by chemical modification and some vehicles.

METHODS

The solubility was examined for different vehicles. The improvement of gastrointestinal absorption was evaluated by the plasma concentration after oral administration to mice or the in situ loop method with rats. The in vivo anti-influenza activity was examined using mice infected with the influenza virus and evaluated based on the virus titer in the lung by TCID50.

RESULTS

PEG 400 showed the highest solubility of Stachyflin and its derivative among the vehicles studied. While no viral inhibition was found in the lung after oral administration of 0.5% HPMC suspension of Stachyflin, in vivo anti-influenza virus activity was found with the PEG 400 solution. The absorption of Stachyflin by PEG 400 showed about a fifty-fold increase in AUC compared with that of 0.5% HPMC suspension. Improving the oral absorption of Stachyflin led to an increase in the in vivo anti-influenza virus activity. When the Stachyflin derivative in PEG 4000 was administered orally, there was more enhancement of the oral absorption than with PEG 400. When the aqueous solution of the phosphate ester prodrugs of Stachyflin and its derivative was administered orally, the absorption of the parent compound was improved and in vivo anti-influenza virus activity was found.

CONCLUSIONS

When Stachyflin and its derivatives were administered orally to mice with a solution in PEG and an aqueous solution of their phosphate ester, their oral absorption was improved and in vivo anti-influenza virus activity was observed.

Some relationships between the physical properties of various 3-acyloxymethyl prodrugs of phenytoin to structure: potential in vivo performance implications

Physicochemical properties of neutral N-acyloxyalkyl derivatives of phenytoin in aqueous, organic solvents and simulated intestinal fluid were evaluated. Based on the hypothesis that these low melting prodrugs may have improved physical properties such as solubility and dissolution rate in gastrointestinal fluid, an enhanced bioavailability of these prodrugs may be observed relative to phenytoin. Melting points, aqueous solubilities, and octanol-water (Poct) and cylcohexane-water (Pcyc) partition coefficients of phenytoin and its prodrugs were determined. A simulated intestinal bile salts-lecithin mixture (SIBLM) was also prepared to possibly mimic the intestinal fluid content. Solubility and dissolution rates of phenytoin and its prodrugs were conducted in aqueous buffer and SIBLM. Apparent micelle-water partition coefficients (Kapp) were calculated by using the aqueous and SIBLM equilibrium solubility data. These properties were qualitatively or quantitatively correlated to the alkyl chain length of the prodrugs. The melting points and aqueous solubilities of all the prodrugs were lower than that of the parent compound, phenytoin. The apparent micelle-water partition coefficient increased with an increase in chain length but unlike the octanol-water and cyclohexane-water partition coefficients the relationship was complex. There was a disproportionate increase in the interaction between the micelle and the prodrug with the prodrugs with alkyl groups larger than four carbons. In SIBLM, the solubilities and dissolution rates were increased to a greater extent for the prodrugs than that for phenytoin. The implications are that the bioavailability of phenytoin from these prodrugs may be comparable to or higher than that of phenytoin despite having lower aqueous solubilities, especially after a meal inducing bile flow.

Improving the oral bioavailability of sulpiride by a gastric-retained form in rabbits

To improve the limited oral bioavailability of sulpiride, a gastric-retained form was developed and evaluated using gastric-emptying-controlled rabbits. The AUC value after oral administration of sulpiride as an aqueous solution was less than that after oral administration of sulpiride original powder. The dissolution was not important as a rate limiting factor for sulpiride oral absorption. Sulpiride was absorbed predominantly from the upper part of the small intestine of the rabbit. A gastric-retained tablet prepared from Carbopol 934P, with sustained-release characteristics, was found to be suitable for improving and extending the oral bioavailability of sulpiride.

Enhanced rectal absorption of itazigrel formulated with polysorbate 80 micelle vehicle in rat: role of co-administered esterase

We investigated the effect of esterase on rectal absorption in the rat of itazigrel using polysorbate 80 (PS-80) micelle as a vehicle to overcome the poor aqueous solubility of itazigrel. The itazigrel formulation prepared with PS-80 increased the absorption compared with a 0.25% carmellose sodium suspension, probably by supplying the itazigrel solute to keep a high concentration at the epithelial surface. When esterase was co-administered with the formulations containing PS-80, the absorption of itazigrel from rat rectum was accelerated further, by rapid release of itazigrel from the micelle vehicle after enzymatic degradation of the PS-80 micelle.

Modification of the dissolution behaviour of a water-insoluble drug, naftazone, for zero-order release matrix preparation

The preparation of hydrophilic matrix tablets able to release naftazone, a water-insoluble drug, into an aqueous medium at a constant rate (zero-order dissolution) is described. Enhancement of dissolution rate of the drug was achieved using cross-linked carmellose sodium, beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin. Hypromellose was used as a water-gelling polymer. Tablets could be prepared that released naftazone at a constant rate over 16 h.

Effects of surfactants on the permeability of canine oral mucosa in vitro

The effect of 3 cationic, 1 anionic, and 1 non-ionic surfactant on the permeability of oral frenulum removed from anesthetized dogs was determined in vitro. Permeability to 12 organic compounds was measured in the presence and absence of surfactant. Cetylpyridinium chloride, cetyltrimethylammonium bromide, benzalkonium chloride and sodium lauryl sulfate, at concentrations from 0.025-1.0% caused dose-related increases in permeability to each of the solutes tested, whereas polysorbate 80 caused an increase in permeability to only 3 solutes, and this occurred only at the highest surfactant concentration employed.

Bioavailability studies with etodolac in dogs and man

The effects of formulation, particle size, coadministration of food, antacids, or antiulcer agents on the bioavailability of etodolac (ULTRADOL, 1,8-diethyl-1,3,4,9-tetrahydropyrano[3,4-b]indole-1-acetic acid), a novel non-steroidal anti-inflammatory agent, have been evaluated in dogs and man. The effects of dosage regimen and/or repetitive dosing on bioavailability were also determined. In man, capsule and tablet dosage forms containing micronized etodolac were shown to have a bioavailability (AUC) equal to that of the reference etodolac solution. Etodolac from tablets and capsules was rapidly absorbed since only minor decreases in Cmax and increases in tmax were observed compared to the etodolac solution. In a comparison of regular and micronized etodolac dosage forms, both in dogs and man, similar findings, i.e. no change in AUC but small parallel changes in Cmax and tmax, were noted. Administration of etodolac with food had no effect on etodolac bioavailability in dogs but tended to cause a delay in its absorption. Coadministration of an antacid, magaldrate, or the antiulcer agent, sucralfate, had no effect on the bioavailability of etodolac in dogs, although with the latter, a significant reduction in Cmax was noted. In man, etodolac may be administered as a single bolus dose or in divided (b.i.d.) doses without any loss in bioavailability. With either regimen, on repeat administration for 7 days, no etodolac accumulation was noted.

Spherical Crystallization: Direct Spherical Agglomeration of Salicylic Acid Crystals During Crystallization

Direct spherical agglomeration of salicylic acid crystals during crystallization is described. The needle-like salicylic acid crystals simultaneously form and agglomerate in a mixture of three partially miscible liquids, such as water, ethanol, and chloroform, with agitation. The agglomerates can be made directly into tablets because of their excellent flowability. Spherical crystallization could eliminate the usual separate agglomeration step after crystallization and may be adaptable to other pharmaceutical and chemical systems.

Studies on the absorption of practically water-insoluble drugs following injection VI: Subcutaneous absorption from aqueous suspensions in rats

The absorption characteristics and kinetics of practically water-insoluble drugs following subcutaneous injection of their aqueous suspensions were investigated in intact rats by the local clearance method and compared with those following intramuscular injection reported previously. The plot of the cube root of the residual fraction of the drug in the injection site versus time gave a good linear relationship under various experimental conditions. The absorption rate constant (j) increased with decreasing particle size. This increase was remarkable in the region of mean particle diameter less than 2-3 micrometers, while it was gradual or slight in the region above this. This phenomenon was explained by the fact that the in vivo spreading of particles of more than approximately 3 micrometers was still more limited by the network of the fibrous tissues. Between j and the initial drug concentration (C0) or injection volume (V0), the practically important relationship j alpha C0g V0h (g = -0.66 and h = -0.32) could approximately be derived from the experimental results. Comparison of j values among various compounds with different solubility (C's) in saline but with similar colloidal properties (particle size distribution and sedimentation volume) showed that a log j versus log C's plot gave a nearly straight line with a slope of approximately 0.5. All the results observed for the subcutaneous absorption were similar to those for intramuscular absorption and could reasonably be explained by the kinetic model proposed for intramuscular absorption.

Oral versus vaginal absorption in oestradiol in postmenopausal women. Effects of different particles sizes

Crystalline oestradiol-17 beta is poorly absorbed from the gastrointestinal tract. Three different fractions and a standard fraction containing oestradiol- 17 beta of a known particle size and surface area, were administered orally, to postmenopausal women, to test if changes in particle size will influence the absorption. The bioavailability of each fraction was determined by measurements of peripheral plasma oestrogens. Two different dosages of the standard fraction were given vaginally to compare the bioavailability after oral and vaginal administration. The gastrointestinal absorption was dependent of the particle size of oestradiol. The smaller particle the more rapid and effective absorption as reflected by increasing area under the plasma concentration curve of oestrone and oestradiol. The smallest particle, however, resulted in a pronounced initial oestradiol peak. The coarser particles were more slowly absorbed with more even plasma oestrogen elevation for a sustained period of time. The vaginal absorption of oestradiol was more effective than the gastrointestinal. When the same amount of an equal preparation according to particle size, was given vaginally the maximal plasma concentration was almost 40 times higher than when given orally.

Dependence of area under the curve on proquazone particle size and in vitro dissolution rate

The in vitro dissolution and GI absorption of various sieve fractions of proquazone were studied (particle-size ranges of 45-74, 160-300, and 500-1000 micrometer). The dissolution rates of preparations F45, F160, and F500 were determined in vitro in a flow-through assembly in artificial gastric juice at 37 degrees. The time required for 63% of the maximum amount of soluble drug to pass into solution was characterized by the dissolution variable tau D. The in vitro dissolution rates for the preparations differed significantly in the order tau D, F45 less than tau D, F160 less than tau D, F500. After oral administration of 300 mg of the fractions to each of eight rhesus monkeys, the area under the plasma level-time curve (AUC) differed significantly in the order AUC F45 greater than AUC F160 greater than AUC F500. The dissolution rate increased with decreasing particle size. The AUC increased with decreasing particle size and with increasing dissolution rate. These results indicate that the dissolution rate probably determines the extent of absorption when dissolution is rate limiting.

Effect of particle size on ophthalmic bioavailability of dexamethasone suspensions in rabbits

Three suspensions of 0.1% [3H]dexamethasone were prepared with mean particle sizes of 5.75, 11.5, and 22.0 micron. The suspensions were dosed topically to the right eyes of rabbits. Their bioavailability was compared by measuring aqueous humor and corneal levels over 5 hr. A statistically significant rank-order correlation was observed between increasing drug levels and decreasing particle size.